The present invention relates to an apparatus for wrapping groups of rolls of products with a sheet of plastic film to form a pack which preferably has a carry handle.
In particular, the present invention is for the production of packs or bundles containing a number of rolls and/or bundles with a rather high closing side.
Said packaging of groups of rolls of paper products, for example toilet or kitchen rolls, is performed using apparatuses designed (see also FIG. 1 which illustrates a known example of a pack):                to automatically wrap sheets 2 of plastic film (such as polyethylene or the like) around the side surfaces of rolls R arranged in an orderly way in one or more rows;        to then close the lower surface P1 of the bundle P by folding the end flaps of the sheet 2 of film over the bottom surfaces of the rolls R contained in the bundle P; and        to seal the folded flaps together;        to feed the partially closed pack, with a stepping motion, so as to fold the film on the front sides P2 and P3 of the pack and        to seal the front sides to form the closed pack.        
This method is implemented using known apparatuses comprising:                a station for feeding individual rolls consisting of movement chutes and bars for pushing the rolls towards a        station for collection of the rolls and formation of the group of products (single or multi layered and in several rows) consisting of an elevator which transfers the products received in an orderly way from the feed station to a        packaging station, at a different level to the feed station and the elevator.        
The elevator operates by means of a table which receives and transports products, which is horizontal and moves vertically between two end levels: the lower level being at the feed station and the upper level being at a section above for insertion of the products in the packaging station where the film is positioned horizontally so that it is intercepted by the products arriving and wraps around them.
Arranged vertically one after another after the sheet of film there are side folding hoppers and units which feed along the pack which is produced in stages, to obtain the first lower closure of the pack on the surfaces, as indicated above, using sealing bars and, in subsequent steps, also closing of the front of the pack.
It is possible to add to such apparatus, for example for bundles with dimensions such that they contain a large number of rolls, the application of a strip, again made of a plastic film, whose ends are fixed to the two sides of the bundle at one of the two front surfaces and whose length is such that it can be used as a handle for picking up and carrying the bundle.
An alternative for the production of “large” bundles, with sealed closure, preferably with the application of a bundle carry handle (automatically and at a cost lower than before) is illustrated in patent application BO2002A000392 by the Applicant, in which a method for creating a closure (with handle) on the packs is performed using an apparatus comprising two plates, which move vertically in opposite directions to bring together the opposite flaps of the sheet of plastic film at one of the two front surfaces of the bundle. These plates keep the flaps stretched out relative to one another with the possibility of sliding at a tangent to the plates, whilst pusher means neatly push the material of the side surfaces of the sheet located between the flaps into the space between the two flaps, gradually as they are brought together.
The plates are also equipped with sealing means for joining the two flaps once they have been brought together, and means designed to make an opening in the surface at which the two flaps are joined, so as to form a handle where necessary.
Said system therefore allows the bundle to be sealed and closed during the stepping feed of the bundle supporting teeth unit, if necessary forming the carry handle by adding, at the side of the path followed by the teeth, a pair of mobile plates on either side of the path to perform said closing.
However, now the current machines producing “standard” bundles have high productivity in terms of time, with consequent greatly reduced dwell periods for pressing the film, sealing and if necessary creating the handle opening, not sufficient to allow said operation. This is because a strictly predetermined time is required, in which at least the packaging station, therefore the conveyor teeth, must be in the dwell state.
Therefore, said factor would limit the maximum productivity of the machine.